Pressure reducing nozzles for pressure guns

ABSTRACT

A pressure reducing nozzle for a pressure gun of the type which discharges a jet of air for cleaning and blowing away purposes. When air pressure guns are used with an air supply in the range of 100 to 125 P.S.I., a means for reducing the effective pressure of the jet discharged from the pressure gun is necessary. The present invention is a two-stage pressure reducing nozzle which is fitted to the vent of a pressure gun. A short tube is located at the entrance of the passageway of the pressure reducing nozzle. The entrance end of this tube is reduced in diameter to form a restrictive orifice and to create a first stage of pressure reduction within the tube. The exit end of this tube is also reduced in diameter to form a second restrictive orifice and to create a second stage of pressure reduction within the passageway of the pressure reducing nozzle downstream from the tube. A vent in the passageway at this tube aides in forming the second stage pressure reduction.

United States Patent Clark PRESSURE REDUCING NOZZLES FOR PRESSURE GUNS [76} Inventor: James T. Clark, 118 W. Railroad Ave., Fort Morgan, Colo. 80701 22 Filed: Dec.4, 1972 21 Appl. No; 311,693

Primary Examiner-M. Henson Wood, Jr. Assistant ExaminerMichael Y. Mar Attorney, Agent, or Firm-Frank C. Lowe [111 3,814,329 June 4, 1974 [57] ABSTRACT A pressure reducing nozzle for a pressure gun of the type which discharges a jet of air for cleaning and blowing away purposes. When air pressure guns are used with an air supply in the range of I00 to 125 P.S.l., a means for reducing the effective pressure of the jet discharged from the pressure gun is necessary. The present invention is a two-stage pressure reducing nozzle which is fitted to the vent of a pressure gun. A short tube is located at the entrance of the passageway of the pressure reducing nozzle. The entrance end of this tube is reduced in diameter to form a restrictive orifice and to create a first stage of pressure reduction within the tube. The exit end of this tube is also reduced in diameter to form a second restrictive orifice and to create a second stage of pressure reduction within the passageway of the pressure reducing nozzle downstream from the tube. A vent in the passageway at this tube aides in forming'the second stage pressure reduction.

6 Claims, 5 Drawing Figures PRESSURE REDUCING NOZZLES FOR PRESSURE GUNS This invention relates to air blowing apparatus com monly known as pressure guns," and more particularly to pressure reducing nozzles for pressure guns.

Pressure guns are useful for many purposes around a shop, a common use being to blow cuttings, dust and the like from shop work and tools as for a cleanup. Sometimes a simple valve with a jet nozzle is used on an air line for such purposes, but pressure guns are preferred. Such pressure guns may be similar to a simple valve and jet nozzle in form, but they are also shaped like a pistol with a control valve trigger.

Most shops are equipped with compressed air lines having a number of connection points, and thus it is no problem to connect a pressure gun into a shop air line at any suitable location as with a conventional snap-on type of a line connector. One problem exists, however, in using pressure guns in the ordinary factory or shop, because the compressed air lines will have an air pressure varying from 100 to 125 P.S.l. (pounds per square inch) in order to operate various types of equipment such as air impact wrenches. However, the effective pressure of the air flow or jet from a pressure gun must be much less than this, and preferably in the order of 30 P.S.l. Not only does a high pressure air flow create a hazard because particles such as cuttings are picked up by the air jet and impelled at such high velocities as to be dangerous and capable of causing injury, but also, the noise level of a high pressure air jet can be unreasonably high and to the point where it is unbearable. This problem of excessive pressure in an air line for a pressure gun is well recognized even to the point where provisions in federal laws concerning safety and health require that the effective pressure of a jet of air from a pressure gun shall not exceed 30 P.S.l.

This means that in every shop where pressure guns are used and where the compressed air supply is in the order of l to 125 P.S.l., there must be some provision for reducing the effective pressure of the jet from the air gun to a value not exceeding 30 P.S.l. This can be an expensive proposition where many outlets in the air lines are involved, since reliable pressure reduction valves can be quite expensive. Also, there can be a substantial expense and nuisance in changing the fittings in a compressed air line every time other air operated equipment and pressure guns are alternatively used at the same connection point.

Various types of pressure reducing nozzles have been proposed for reducing the effective pressure of the air flow from a pressure gun and these nozzles are generally formed as aspirators. Basically, a small diameter jet of high velocity air is discharged into a vented tube to expand within the tube and to discharge therefrom along with additional air which is effectively pumped through the tube by the jet. Although a pressure reduc ing nozzle contructed according to this principle is a substantial improvement over a nozzle discharging an unrestrained high pressure air jet, the types presently available are not completely successful inreducing the noise level and in functioning in a satisfactory manner, especially whenever air pressure varies at the high pressure source or whenever the discharge end of the nozzle is accidentally plugged. it follows that there is a real and definite need for an improved pressure reducing nozzle to reduce the effective pressure of a jet from a pressure gun and to provide for more reliable and a quieter performance of the pressure gun to better comply with the newly passed safety and health laws.

The present invention was conceived and developed with such considerations in view and comprises. in essence, a novel construction of a pressure reducing nozzle which is connected to the vent of a pressure gun. This improved nozzle reduces the effective air pressure discharged from the pressure gun and does so in a surprisingly quiet manner. First stage and second stage jet expansion sections are provided within the nozzle to reduce the effective pressure of the air flowing through the nozzle in two steps, with the second stage pressure reduction being supplemented by air from the atmosphere which enters the nozzle through vents. Not only does this two-stage, pressure reducing nozzle function to reduce the effective pressure of a jet discharged from it, but also, other advantages become apparent in operating a pressure gun with this pressure reducing nozzle at its vent. The jet discharged from it is far more stable and a much quieter operation results. Moreover, neither a build-up of pressure nor objectional noise will occur if the nozzle is plugged.

It follows that an object of the invention is to provide a novel and improved pressure reducing nozzle for a pressure gun which permits the gun to be connected directly to a compressed air line without the necessity of special fittings and pressure reducing valves, and which is an integral unit having no moving parts nor parts requiring adjustment and maintenance.

Another object of the invention is to provide a novel and improved pressure reducing nozzle for a pressure gun attached to a high pressure air supply which discharges an air jet from the gun at a safe, reduced pressure at a greatly reduced noise level and will not cause a pressure build-up if the exit end of the nozzle is accidentally plugged.

Another object of the invention is to provide a novel and improved two-stage pressure reducing nozzle for an air gun attached to a high pressure air supply which not only reduces the effective pressure and velocity of a jet of air discharged from the nozzle, but also provides for a better control of the air flow through the gun.

Other objects of the invention are to provide a novel and improved pressure reducing nozzle'for a pressure gun which is a simple, economical, rugged, durable and reliable unit.

With the foregoing and other objects in view, all of which more fully hereinafter appear, my invention comprises certain constructions, combinations and arrangements of parts and elements as herein described, defined in the appended claims, and illustrated in preferred embodiment in the accompanying drawing in which:

FIG. 1 is a side elevational view of a typical pressure gun which is connected to a high pressure air hose and which has the improved pressure reducing nozzle mounted at the vent end of the gun.

FIG. 2 is a side elevational view of the vent end of the gun and of the upper section of the pressure reduction nozzle mounted at this end, the view being an enlargement of a portion of FIG. 1.

FIG. 3 is a longitudinal sectional view as taken from the indicated line 3-3 at FIG. 2, but on an enlarged scale.

FIG. 4 is a transverse section as taken from the indicated line 4-4 at FIG. 2, but on an enlarged scale.

FIG. 5 is a longitudinal sectional view similar to FIG. 3, but on an enlarged scale illustrating, diagrammatically, the manner in which air flows through the unit.

Referring more particularly to the drawing, FIG. 1 illustrates a conventional pressure gun G which is connected-to a high pressure air line L. The invention resides in a pressure-reducing nozzle N located at the vent, or exit, of this pressure gun G. The gun G is suitably formed as a pistol having a handle and a barrel 1]. A trigger 12 is located at the crotch between the handle and barrel. A passageway 13, shown in dotted lines, extends through the handle 10 and through the barrel 11. This passageway 13 is intercepted by a normally closed valve 14, also shown in dotted lines, and the valve 14 is opened by pressing the trigger 12 to permit an air flow through the gun. Some regulation of air flow is possible at this valve, and stop 15 is mounted upon this trigger to regulate the opening of the valve.

The air pressure line L has a threaded coupling 16 at its end, and this line connects with the passageway 13 either at the base of the handle 10 as illustrated, or at the rear end of the barrel 11 where threaded sockets 17 are provided to receive the coupling 16. A plug 18 closes the passageway at the threaded socket 17 which does not connect with the pressure line. A pressure gun may be simplified over the construction shown by eliminating the handle 10, so that the gun will consist of the barrel and a suitable trigger. However, the basic features of the vent end of the gun are unchanged and the pressure reducing nozzle, as hereinafter described, may be used with both types.

The diameter of the passageway 13 in the handle and through the barrel is sufficient to permit a free flow of air through the gun when the valve 14 is open. A suitable passageway in a conventional air gun may be from Vs-inch to approximately 3/l6-inch. The free flow of air can easily produce a flowing jet at the vent of the gun whose velocity approaches the full velocity which can be produced by the effective pressure available in the line L. Thus, when the effective pressure head in the line L is 100 P.S.l., or more, the resulting velocity of the jet is excessive for ordinary use and is also very noisy.

The only control which is imposed upon the air flow through this conventional gun G is at the trigger 12 which opens the valve 14. Such a control has been found to be of limited value, and the valve is not especially reliable in reducing the effective flow pressure or the velocity head of the jet.

The present invention provides for a pressure reducing nozzle N at the vent of the pressure gun, and this nozzle becomes an integral part of the pressure gun whenever the gun is in use. The nozzle N is a longitudinally extended, tubular member having a threaded stub 20 at its leading end which permits it to be turned into a corresponding threaded socket 21 at the vent of the gun, as best illustrated at FIGS. 1 and 3. The threads used on the stub and in the socket are preferably a type which fit tightly to eliminate the need for gaskets. However, the nozzle may be fitted into the gun barrel using different thread types or in any other suitable manner, or it may even be an integral part of the gun barrel 11.

The nozzle N includes a head 22 at its leading end and an extension tube 23 at its trailing end. The head 22 has the general appearance of an ordinary tubing fitting. A central section 24, which is preferably hexagonal in cross section, carries the threaded stub 20 at its leading end, or upstream end, with respect to the direction of air flow. The trailing end, or downstream end. of this central section is formed as a conical, tapered sleeve 15. The extension tube 23 is telescopically fitted into a cylindrical socket 26 in this sleeve 25, as illustrated at FIGS. 3 and 5. A passageway 27 within this tube extends a short distance within the central section 24 of the head 22 and this passageway defines a second-stage expansion section as hereinafter further described.

This extension tube 23 may be comparatively short, say no longer than the sleeve 25, which is sufficient to assure expansion of a jet as will be described. The tube may be several inches long, as illustrated, but it may also be of an extended length, a foot or more. Also, this tube may be either a rigid or flexible member. The extension tube 23 may be fitted into the cylindrical socket 26 as by a simple frictional fit if it is to be changed from time to time, or, preferably, it may be permanently affixed in the sleeve as by soldering.

The passageway 27 through this nozzle and into the downstream portion of the head 22 is centered at the longitudinal axis of the nozzle. An axially centered tubular opening 28 extends through the upstream end of the head 22, that is, the section which includes the stub 20 and the upstream portion of the central section 24. The diameter of this opening 28 is less than the diameter of the passageway 27. A short, tubular member, forming a first stage expansion chamber tube 29, is tightly fitted in this reduced diameter section, and preferably, this chamber tube 29 in the passageway 27 is soldered in place. The upstream end of this chamber tube 29 is reduced in diameter to form a first stage orifice 30 wherethrough a small diameter jet of air will flow. The downstream portion of the chamber tube 29 extends beyond the reduced-diameter tubular opening 28 to cantilever within the passageway 27, with an annulus 31 being defined by the space between the passageway 27 and the cantilevered portion of the chamber tube 29. The downstream end of this chamber tube is also reduced in diameter to form a second stage orifice 32 wherethrough a small diameter jet of air will flow; however, it is to be noted that this second stage orifice 32 is larger in diameter than the first stage orifice 30.

To complete this pressure reducing nozzle, two or more transversely disposed, opposing vents 33 extend through the head 22 in the section where the annulus 31 is situated. The size of the openings is such that the area of the annulus is less than the area of the vent openings so that a flow control is at the annulus and thus variations of vent size or any rough edges or solder globs which might appear in the manufacture of the unit will not affect the flow characteristics of the air entering the vents.

The proportions of the nozzle N, including its length, and the diameters of the passageway 27, the inside of the chamber tube 29, the first stage orifice 30, the second stage orifice 32 and vents 33, are selected to produce an action which in the science of fluid mechanics is sometimes referred to as the sudden expansion of a jet with an accompanying loss of effective pressure and velocity head. Such an expansion will occur a short distance downstream from where the jet is formed.

Referring to FIG. 5, one expansion will occur in the first stage chamber tube 29 to reduce the high pressure air from the line L and through the gun. A jet J1 flows through the orifice 30 to expand suddenly within the first stage chamber C. The air, then reduced in velocity, flows through the tube 29 to be discharged from the orifice 32. The resulting jet J2 is in the second stage of flow, into the passageway 27 where another sudden expansion will occur as illustrated, so that the air is further reduced in velocity as it flows from the tube 23. In this second stage expansion, however, the sudden expansion of jet 12 is accompanied by a flow of air through the vents 33 to further help in reducing the pressure of the air jet and to let the atmospheric air supplement the flow of air from the nozzle N.

The effective pressure of the jet which is discharged from the nozzle can be established at any selected value when the air pressure in the line L and the dimensions of the passageway 27 and the chamber tube 29 are known. Once the proportions of the air gun are selected, the pressure at the exit of the nozzle will depend upon the diameter of the orifice 30, the diameter of the orifice 32 and the air pressure in the line L. Simple tests can establish a desirable orifice diameter, but such may also be determined by computations. This expansion action is well-known to those skilled in the art and need not be described here in detail.

in one commerical application, the pressure gun G is manufactured as a standard unit having a barrel length of approximately 6 inches. The nozzle, including its head 22, will have a length of approximately 4 inches and the extension tube will have a A-inch inside diameter. The inside diameter'of the tube 29 may be /ainch. The diameter of the first stage orifice 30 will be somewhat less than l/ 16-inch and the diameter of the second stage orifice will be approximately 3/32-inch.

Once the air pressure in the line L is specified, a pres sure gun can be provided with a nozzle N which will restrict the effective discharge pressure to not'more than 30 P.S.I. The pressure gun with this nozzle will operate quietly, yet the jet will have enough force to effectively blow away dust and particles when cleaning a bench or a work piece. Other desirable advantages are obtained by using a pressure gun with the pressure reducing nozzle N. It is a safe tool to use. Even though the exit of the extension tube were to be accidentally closed or plugged, a build-up of air pressure cannot occur, because air will then be discharged from the vents 33. This can be very important should the air gun be accidentally pressed against a tender part of a persons body, such as against his ear. Another advantage resides in the fact that the amount of high pressure air used is a very minimum, because the small diameter jet of high pressure air will aspirate a substantial amount of atmospheric air through the vents to form the jet discharged from the nozzle.

A further unexpected advantage to the unit resides in the very effective control possible by use of the trigger 12. While the valve 14, controlled by the trigger 12, is not at all effective in reducing the air pressure in controlling the air flow through the gun without the nozzle, the control action is literally magnified by the effect of the two-stage sudden expansion of air jets from the orifices 30 and 32 because slight changes in velocity of the jets through these orifices can produce significant changes in the pressure at the discharge end of the nozzle.

l have now described my invention in considerable detail; however, it is obvious that others who are skilled in the art can devise and build alternate and equivalent constructions which are in the spirit and scope of my invention. Hence, I desire that my protection be limited, not by the constructions illustrated and described, but only by the proper scope of the appended claims.

I claim:

l. A two-stage pressure reducing nozzle for a pressure gun connected to a high pressure air line, to reduce the velocity of air flow from the vent of the pressure gun, and comprising:

a. a lo r 1 gi tud inall y extended chamber at the upstream end of the nozzle with respect to the air flow, with the upstream end of the chamber being at the vent of the pressure gun when the nozzle is attached to the pressure gun;

b. a longitudinally extended passageway at the downstream end of the nozzle, with the upstream end of the passageway connecting with the downstream portion of the chamber and the downstream end of the passageway being open to permit a jet of air to flow therefrom;

c. a first-stage orifice at the upstream end of the chamber wherethrough a high velocity jet bran may flow, from the pressure gun vent and into the chamber; and

d.a second-stage orifice at the downstream end of the chamber, wherethrough a reduced velocity jet of air may flow, from the chamber and into the passageway; and

wherein the diameter of the first-stage orifice is correlated with the diameter of the chamber to produce a first-stage sudden expansion of air flow from the high velocity jet to occur within the chamber and the diameter of the second-stage orifice is correlated with the diameter of the passageway to produce a second-stage sudden expansion of air flow from the reduced velocity jet to occur within the passageway.

2. In the pressure reducing nozzle defined in claim 1,

including:

air vents in the upstream portion of the passageway which is upstream from the point where the second-stage sudden expansion of air flow occurs.

3. In the pressure reducing nozzle defined in claim 1, wherein:

the passageway has a diameter greater than the diameter of the chamber;

the downstream portion of the chamber is a thinwalled member which extends into the upstream end of the passageway with an annulus space in this passageway about the downstream portion of the chamber; and

air vents are in the passageway at this annulus space.

4. In the combination defined in claim 1, wherein:

the nozzle includes a head section adjacent to the gun; and

a tube is attached to the head section and extends to the exit of the nozzle to define the major reach of said passageway.

5. in the pressure reducing nozzle defined in claim 4,

wherein:

said chamber is formed as a tubular member fitted into an opening in the head with the upstream end of the member being at the upstream end of the head.

7 8 6. In the pressure reducing nozzle defined in claim 5, projects into the passageway to form an annulus wherein: space therein; and

said chamber member has a diameter less than said air vents open in the passageway at said annulus passageway; space.

the downstream portion of said chamber member 

1. A two-stage pressure reducing nozzle for a pressure gun connected to a high pressure air line, to reduce the velocity of air flow from the vent of the pressure gun, and comprising: a a longitudinally extended chamber at the upstream end of the nozzle with respect to the air flow, with the upstream end of the chamber being at the vent of the pressure gun when the nozzle is attached to the pressure gun; b a longitudinally extended passageway at the downstream end of the nozzle, with the upstream end of the passageway connecting with the downstream portion of the chamber aNd the downstream end of the passageway being open to permit a jet of air to flow therefrom; c a first-stage orifice at the upstream end of the chamber wherethrough a high velocity jet of air may flow, from the pressure gun vent and into the chamber; and d a second-stage orifice at the downstream end of the chamber, wherethrough a reduced velocity jet of air may flow, from the chamber and into the passageway; and wherein the diameter of the first-stage orifice is correlated with the diameter of the chamber to produce a first-stage sudden expansion of air flow from the high velocity jet to occur within the chamber and the diameter of the second-stage orifice is correlated with the diameter of the passageway to produce a second-stage sudden expansion of air flow from the reduced velocity jet to occur within the passageway.
 2. In the pressure reducing nozzle defined in claim 1, including: air vents in the upstream portion of the passageway which is upstream from the point where the second-stage sudden expansion of air flow occurs.
 3. In the pressure reducing nozzle defined in claim 1, wherein: the passageway has a diameter greater than the diameter of the chamber; the downstream portion of the chamber is a thin-walled member which extends into the upstream end of the passageway with an annulus space in this passageway about the downstream portion of the chamber; and air vents are in the passageway at this annulus space.
 4. In the combination defined in claim 1, wherein: the nozzle includes a head section adjacent to the gun; and a tube is attached to the head section and extends to the exit of the nozzle to define the major reach of said passageway.
 5. In the pressure reducing nozzle defined in claim 4, wherein: said chamber is formed as a tubular member fitted into an opening in the head with the upstream end of the member being at the upstream end of the head.
 6. In the pressure reducing nozzle defined in claim 5, wherein: said chamber member has a diameter less than said passageway; the downstream portion of said chamber member projects into the passageway to form an annulus space therein; and air vents open in the passageway at said annulus space. 